I need some advice to help track down my biological grandmother. My father was adopted in 1920 and died in 2000 without knowing the identity of his biological parents. I have his birth certificate but I am not certain that the name of his mother is her real name. I DNA tested with Ancestry and found 1000+ matches. To my surprise, one shared 1752 centimorgans with me. By process of elimination, he has to be a hitherto unknown half-brother. I am certain he is on my father’s side because none of my cousins on my mother’s side who tested with Ancestry share matches with him. I have tried to contact him but have not heard from him. It would be nice if I could have him upload his raw data to GEDMatch but I do not expect to hear from him. I did find matches for people at 222, 169, 140, 64, and 60 centimorgans all of whom were kind enough to allow access to their family trees. By filling out my tree with their information I was able to locate my paternal grandfather. All of these people fell into the proper place on the genealogy chart based on the centimorgans we share.
On Ancestry there are 5 matches I know to be maternal cousins. I used them to eliminate shared matches leaving what should be paternal matches. I’m not sure if I am on the right track but I also eliminated those that matched with the half-brother leaving matches that, theoretically, should only be to my paternal grandmother’s family.
Am I on the right track here or am I missing something?
Additionally, how should I use the information about the half-brother to trace up family trees and back down to find my grandmother?
I’m just not sure how far back to go or what relationship to look for.